A fuel cell cooling device disclosed in Tokkai 2002-352835, published by the Japan Patent Office in 2002, controls the amount of water conveyed by a conveying pump and the amount of heat generated by a heater for preventing the freezing of cooling water on the basis of the temperature of the cooling water in the fuel cell and the differential pressure of the cooling water. The fuel cell cooling device comprises a water temperature sensor which detects the temperature of the cooling water and a differential pressure gauge which detects the differential pressure between the cooling water inlet and outlet of a fuel cell stack.